With the development of information/data storage with magnetic means, cards with a magnetic tape fixed thereon to store data have been widely used, such as personal identification cards, credit cards, bank auto-teller cards and even driver's licenses. To access information/data stored in the magnetic tape attached to a card, a device to read and/or write data from/to the magnetic tape, which will be referred to as card reader, is very important in developing such a system.
The card readers currently available are classified into two types: read-only and read-and-write. The read-only card reader is only capable to read the magnetic tape on the card, while the read-and-write card reader is capable of both reading and writing operations. In a read-and-write card reader, the reading/writing operation is achieved by providing a roller which rotates in unison with the movement of the card through a card slot. An encoder is attached to the roller so that in the movement of the card through the card slot, the encoder generates encoding signals at every given distance of displacement of the card so as to instruct a write transducer to write data to correction locations on the magnetic tape. The locations of the magnetic tape on which the data are written have to be very precise, otherwise a read transducer would not be able to read the data correctly or the data density that the magnetic tape may have data stored thereon has to be decreased for read transducer reads the data at locations with a predetermined gaps therebetween.
A conventional read-and-write card reader is shown in FIGS. 5 and 6 of the attached drawings which comprises a base A on which two spaced walls W are mounted to define therebetween a card slot F through which a card is to be moved. A write transducer B and a read transducer H are suspended on one of the walls W by steel plates D and J to be partially project into the card slot F through openings formed on the wall W so that when the card is moved through the card slot F, the transducers B and H are capable to engage the magnetic tape on the card for writing and reading operations. An encoder G is mounted to the other one of the walls W by means of a cantilever arm C which has one end fixed to the other one of the walls W and another end free with the encoder G rotatably supported thereon. The encoder W is located so as to be opposite to the write transducer B and partially project into the card slot F to be engageable by the card in moving through the card slot F. The movement of the card drives the encoder W to rotate and thus generate desired encoding signal.
A disadvantage associated with the conventional card reader is that the cantilever arm C is subject to deflection due to the card forced into between the encoder G and the write transducer B which rotates the free end of the cantilever arm C on which the encoder G is supported an angle .theta. relative to the anchored end that is fixed to the wall W. Such a deflection angle .theta. causes error in the encoding operation for the deflection angle .theta. is the result of combination of movement of the encoder G in both a direction normal to the movement of the card and a direction parallel with the movement of the card and thus the position of the encoder G is changed by the insertion of the card between the encoder G and the write transducer B not only in the direction normal to the movement of the card, but also in the direction parallel with the movement of the card. The distance between two successive locations within the magnetic tape on which data are written is increased by the occurrence of the deflection angle .theta..
To reduce the negative influence of the deflection angle .theta., it has been suggested to increase the length of the cantilever arm C, as shown in prior art design of FIG. 7 of the attached drawings so as to reduce the position change in the direction of the movement of the card. This, however, is not possible to overcome such a problem.
Further, due to the cantilever type suspension of the encoder, the encoder is easily subject to the problem of vibration induced on the cantilever arm and the longer the cantilever arm, the more serious the vibration problem. Such a vibration may cause wearing and abrasion on the write transducer and the magnetic tape of the card.
It is therefore desired to provide a card reader which overcomes the problems encountered in the prior art card reader designs.